变量说明:
$$ Shell本身的PID（ProcessID）
$! Shell最后运行的后台Process的PID
$? 最后运行的命令的结束代码（返回值）
$- 使用Set命令设定的Flag一览
$* 所有参数列表。 所有的参数被认为是一个字符串
$@ 所有参数列表。参数是独立的字符串
$# 添加到Shell的参数个数
$0 Shell本身的文件名
$1～$n 添加到Shell的各参数值。$1是第1个参数、$2是第2个参数…。
通过一个脚本，来看看各个变量的效果
1 #!/bin/sh 2 3 ## RustFisher 4 5 echo "----------------------" 6 echo "PID: \$$ $$" 7 echo "option numbers: \$# $#" 8 echo "last return: \$? $?" 9 echo "all parameters: \$* $*" 10 echo "all parameters: \$@ $@" 11 echo "file name: \$0 $0" 12 echo "1st param: \$1 $1" 13 echo "2nd param: \$2 $2" 14 echo "3rd param: \$3 $3" 15 echo "4th param: \$4 $4" 16 echo "9th parem: \$9 $9" 17 echo "-----------------------" 18 19 index=1 20 21 echo "get args by \"\$@\":" 22 23 for arg in "$@" 24 do 25 echo "Arg #$index=$arg" 26 let "index+=1" 27 done 28 29 echo "-----------------------" 30 31 index=1 32 33 echo "get args by \"\$*\":" 34 35 for arg in "$*" 36 do 37 echo "Arg #$index=$arg" 38 done 39 40 echo "-----------------------"
输出结果：
$ sh show.sh dont "worry be" happy ---------------------- PID: $$ 12897 option numbers: $# 3 last return: $? 0 all parameters: $* dont worry be happy all parameters: $@ dont worry be happy file name: $0 show.sh 1st param: $1 dont 2nd param: $2 worry be 3rd param: $3 happy 4th param: $4 9th parem: $9 ----------------------- get args by "$@": Arg #1=dont Arg #2=worry be Arg #3=happy ----------------------- get args by "$*": Arg #1=dont worry be happy -----------------------
